Coupler



FIG. 1 is a rear perspective view of a coupler showing my new design;

FIG. 2 is a front perspective view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a front elevational view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof;

FIG. 7 is a left side elevational view thereof; and,

FIG. 8 is a right side elevational view thereof.

The broken line showing of multiple surface features is included for the purpose of illustrating environmental structure and forms no part of the claimed design. 

The ornamental design for a coupler, as shown and described. 